Some modern communications solutions are based on VoIP (Voice-over IP (Internet Protocol)) technology, which is the transmission of calls over a data network based on the IP. The communication is in the form of packet data and thus there is no fixed connection as there would be in the case of switched networks. The communication can be text, voice, graphics or video. In order to simplify IP communication problems, standards have been developed and adopted in the industry. Examples of such standards are H.323 (Packet based communication systems) and SIP (Session Initiation protocol). These standards are followed when designing new hardware and software. The SIP standard covers the technical requirements to set-up, modify and tear down multimedia sessions over the Internet. A multimedia communication session between two endpoints will be referred to as a call.
Communication solutions, whether they be switch based or packet based, are defined and designed for a specific number of users and call processing capacity, generally defined by the number of ports (telephone terminations), and the amount of processing available on a central processing equipment that provides routing and call processing functionality. Hence, equipment vendors generally develop and market versions of the same product for different customer size and needs. However, a customer needs to upgrade to larger central processing equipment once the number of ports required and/or call-processing requirements exceed the capacity of the central processing equipment.
Costs associated with processing and memory have made inclusion of a call-processing engine on every telephone set prohibitively expensive. Hence, current multimedia communication systems use a central processing equipment and simple user terminal sets. These simple user terminal sets are referred to as “stimulus terminals” as they simply send user stimuli such as key presses to the central processing equipment. In large systems, the central processing equipment is generally a very powerful computer controlling a number of functions on circuit boards called line cards, which connect telephone sets to the computer. The central processing equipment receives hook-switch information and key presses known in the art as DTMF (Dual Tone Multi-Frequency) tones from the telephone sets, and provides feedback to the telephone sets for example by sending a dial-tone or a ringing tone to the telephone sets. By interpreting the key presses, the central processing equipment controls the interconnection of the telephone sets based on numbers dialed by the telephone sets.
Voice mail has been provided using a centralized voice mail equipment either integrated with or separate from the central call processing equipment. The centralized voice mail equipment is designed and built with a certain voice storage capacity and voice processing capability in which a number of simultaneous calls can be processed and stored at any given time. Again, since buying a large voice mail solution is generally expensive, customers generally start with a smaller voice mail solution, and upgrade to larger solutions when required. Upgrading adds costs and results in operation disruptions.
Another disadvantage of centralized voice mail equipment in a voice mail system is the lack of overall reliability and availability of the voice mail system. When the centralized voice mail equipment fails, the voice mail system is unable to take or retrieve messages. Manufacturers have taken steps to duplicate critical pieces of equipment such as power supplies, CPU (Central Processing Equipment), and disk drives, and in some cases duplicate whole systems to increase the overall availability of the system; however, this, once again, increases overall costs.